对java.io.*;熟的朋友.进来帮帮助

public boolean copyFile(String from,String to){

File fromFile,toFile;

fromFile = new File(from);

toFile = new File(to);

FileInputStream fis = null;

FileOutputStream fos = null;

try{

toFile.createNewFile();

fis = new FileInputStream(fromFile);

fos = new FileOutputStream(toFile);

int bytesRead;

byte[] buf = new byte[4 * 1024];// 4K buffer

while((bytesRead=fis.read(buf))!=-1){

fos.write(buf,0,bytesRead);

}

fos.flush();

fos.close();

fis.close();

}catch(IOException e){

System.out.println(e);

return false;

}

return true;

}

如果B目录可能不存在的话，最好用File里的exists()判一下是不是存在这个目录
A.txt文件的话，也是一个道理

biaoflying() 回答得很好了...

谢谢，各位好友。。。我懂了。。。

import java.io.*;
public class Test
{
public boolean copyfile(String src,String dec)
{
File srcFile=new File(src);
File decFile=new File(dec);

try
{

FileInputStream fis=new FileInputStream(srcFile);
FileOutputStream ops=new FileOutputStream(decFile);
int n;
byte buff[]=new byte[1024*4];
decFile.createNewFile();

while((n=fis.read(buff))!=-1)
{
ops.write(buff,0,n);

}
ops.flush();
fis.close();
ops.close();

}

catch(FileNotFoundException e)
{

System.out.println(e);
}
catch(IOException er)
{

System.out.println(er);
return false;
}
return true;

}

public static void main(String[] args)
{
Num6 cf=new Num6();
String src = "c:/a.txt";
String des = "c:/B/c.txt";
if(cf.copyfile(src,des))
{

System.out.println("拷贝成功");

}
else
{
System.out.println("拷贝失败");
}
}

}